首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5328篇
  免费   182篇
  国内免费   21篇
电工技术   40篇
综合类   12篇
化学工业   1212篇
金属工艺   123篇
机械仪表   96篇
建筑科学   252篇
矿业工程   22篇
能源动力   162篇
轻工业   366篇
水利工程   45篇
石油天然气   18篇
无线电   406篇
一般工业技术   1058篇
冶金工业   867篇
原子能技术   34篇
自动化技术   818篇
  2023年   28篇
  2022年   49篇
  2021年   100篇
  2020年   84篇
  2019年   78篇
  2018年   111篇
  2017年   88篇
  2016年   105篇
  2015年   101篇
  2014年   134篇
  2013年   336篇
  2012年   185篇
  2011年   298篇
  2010年   230篇
  2009年   252篇
  2008年   238篇
  2007年   234篇
  2006年   191篇
  2005年   169篇
  2004年   165篇
  2003年   148篇
  2002年   134篇
  2001年   112篇
  2000年   103篇
  1999年   106篇
  1998年   164篇
  1997年   111篇
  1996年   100篇
  1995年   81篇
  1994年   98篇
  1993年   93篇
  1992年   87篇
  1991年   63篇
  1990年   65篇
  1989年   70篇
  1988年   65篇
  1987年   45篇
  1986年   53篇
  1985年   71篇
  1984年   61篇
  1983年   55篇
  1982年   43篇
  1981年   40篇
  1980年   45篇
  1979年   37篇
  1978年   35篇
  1977年   43篇
  1976年   52篇
  1975年   30篇
  1973年   32篇
排序方式: 共有5531条查询结果,搜索用时 15 毫秒
1.
Quality of service has become today a major concern for operators of mobile communication networks. The massive development of networks and strong competition between operators has lead to the necessary and daily follow-up of network quality of service, a key factor for its subscriber’s fidelity. This article aims at presenting the optimization methodology and proposes its illustration with a case of RNO (Radio Network Optimisation) software usage, one of the Alcatel optimization toolchain component. After a short presentation of cellular network, the optimization basic principles are described. RNO software and its main functionnalities are then detailed before a last part dedicated to a real case of optimization done with RNO software.  相似文献   
2.
Due to the language barrier, non-English users are unable to retrieve the most updated medical information from the U.S. authoritative medical websites, such as PubMed and MedlinePlus. However, currently, there is no any cross-language medical information retrieval (CLMIR) system that can help Chinese-speaking consumers cross the language barrier in finding useful English medical information. A few CLMIR systems utilize MeSH (Medical Subject Headings) to help overcome the language barrier. Unfortunately, the traditional Chinese version of MeSH is currently unavailable.In this paper, we employ a semi-automatic term translation method to construct a Chinese–English MeSH by exploiting abundant multilingual Web resources, including Web anchor texts and search–result pages. Through this method, we have developed a Chinese–English Mesh Compilation System to assist knowledge engineers in compiling a Chinese–English medical thesaurus with more than 19,000 entries. Furthermore, this thesaurus has been used to develop a prototypical system for cross-language medical information retrieval, MMODE, which can help consumers retrieve top-quality English medical information using Chinese terms.  相似文献   
3.
4.
5.
Glucose levels in rats with hyperglycemia induced by streptozotocin were determined after i.p. administration of marsupsin (1), pterosupin (2), and pterostilbene (3), three important phenolic constituents of the heartwood of Pterocarpus marsupium. Marsupsin and pterostilbene significantly lowered the blood glucose level of hyperglycemic rats, and the effect was comparable to that of 1,1-dimethylbiguanide (metformin).  相似文献   
6.
Editorial.     
With this volume, the 47-year old Canadian Journal of Psychology takes a new name and makes a renewed commitment. In retitling the journal the Canadian Journal of Experimental Psychology, the intention is to reflect more clearly what has always been the major goal of the journal--to publish the best new research in experimental psychology, both Canadian and international, in both French and English. I am honoured to become the tenth editor of the major journal for experimental psychology in Canada. CJP has served the field very well; my primary goal is to ensure that CJEP continues to do so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
Colin Hines 《Energy Policy》1985,13(2):188-189
This communication illustrates the work of the London Energy and Employment Network. LEEN has the twin aims of promoting a rational energy policy for London and, in the process, generating much needed employment. In cooperation with Hackney, one of Britain's poorest boroughs, LEEN organized Hackney's Cold War — a series of initiatives showing the practical measures, informational back-up and funding sources necessary for a local energy policy. LEEN intends to repeat this project in other London Boroughs, with the eventual aim of helping to persuade central government to adopt a more comprehensive approach to energy conservation nationally.  相似文献   
8.
The corrosion behaviour of nitrogen-containing austenitic stainless steel in methanol containing different concentrations of H2SO4, HCl, LiCl and H2SO4 + HCl has been investigated using a potentiostatic polarization method. The cathodic reaction in the H2SO4, HCl and H2SO4 + HCl solutions was proton reduction whereas in the neutral LiCl solution, oxygen reduction was the predominant cathodic reaction. Active, passive and transpassive behaviours were observed only for higher concentrations of H2SO4 (0.01–2.0 M) due to the inherent water content. A cathodic loop, characterized by measured negative current in the anodic region, was also observed in solutions, in which the concentration of H2SO4 was 1.0 M or higher. The relative stability of the passive films decreased as the H2SO4 concentration increased, and thus the steel suffered from mild pitting corrosion. In the chloride environment, the rate of corrosion increased as the Cl ion concentration increased. The presence of acid along with Cl ions enhanced corrosion, and the corrosion rate increased significantly. The steel suffered from mild intergranular corrosion in acidic chloride solutions of methanol. In the H2SO4 + HCl solutions, passive films were only formed when the H2SO4 to HCl concentration ratio was greater than ∼10:1.  相似文献   
9.
Choosing a standard speed for visual inspection is difficult using standard work measurement techniques. This paper uses a different approach, taking a model of human functioning in inspection and deriving an optimum speed of working so as to balance the cost of time against the cost of errors. Random search is used as the model and both self-paced and externally-paced conditions are derived for multiple fault types. Optimization using a Golden Section search is used to provide optimum inspection speed.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号